Effects of Cyanide and Acetylcholine on Extracellular K⁺ and Ca⁺⁺ Activities in the Cat Carotid Body

Abstract

At the Seventh International Symposium on Peripheral Arterial Chemoreceptors we reported that close arterial infusion of dopamine (20–50 μg.min^-1) induced either no changes or reductions in extracellular K+([K+]₀) and Ca++ ([Ca++]₀) activities in the cat carotid body (O’Regan and Acker, 1984). Further experimentation has confirmed these findings although in occasional trials [Ca++]₀ elevations rather than reductions accompanied dopamine admininstration. As the major action of dopamine is considered to be inhibition of chemoreceptor activity we felt it would be of interest to compare its effects on [K+]₀ and [Ca++]₀ with those associated with agents which predominantly excite chemoreceptor discharges such as cyanide, acetylcholine and hypoxic hypoxaemia.